Evening Terbs,just seen your thread and i've sent you a PM. I still have a number of these Eternal systems in my store aswell as genuine GM cranks sensors,disc and pad sets,rear shocks,Boge and Suplex rear springs etc.
Most likely down to the first small cats on the downpipe failing, try running e5 petrol and if no better just remove the eml bulb as unless you replace both downpipes inc the cats it will continually occur.
If anyone is interested I have 4 saloon systems and 1 estate system all with twin tail pipes in my spares store. Collection only near J14 M1 £100 per system
I still have 4 complete new eternalcar systems with twin pipe rear in my store and also 1 system for an estate. Collection only from Olney Bucks. 0788102585